Answer
Shared locks permit concurrent reads, while exclusive locks block all reads and writes. Writes always require exclusive locks.
Quick Answer
Shared lock (S lock): multiple transactions can hold shared locks on the same row simultaneously - used for reads. Exclusive lock (X lock): only one transaction can hold an exclusive lock - blocks all other reads and writes. SELECT ... FOR SHARE acquires shared locks. SELECT ... FOR UPDATE acquires exclusive locks. INSERT, UPDATE, DELETE acquire exclusive row locks automatically.
S
SugharaIQ Editorial Team
Verified Answer
This answer has been peer-reviewed by industry experts holding senior engineering roles to ensure technical accuracy and relevance for modern interview standards.
Want to bookmark, take notes, or join discussions?
Sign in to access all features and personalize your learning experience.
Source: SugharaIQ